Nighttime Ventilation questions for newbie..AC or Fan?

this is my second year camping with trailer. we camp in the Adirondacks in NYS... can have warm days and cool nights.. I noticed last year with my new camper that even on nights when it was cool outside that it was always stuffy inside the camper at night.. we would have to close the windows and turn the AC on everynight.. just seems like a waste of electric on cooler nights... opening windows didn't seem to help... the AC unit also has a fan instead, but then the fan would blow all night long, whereas atleast the AC would turn on and off with the digital thermostat...
has anyone else been stuffy inside there TT? any ways around this besides wasting a ton of electric? I can understand hot nights, but not even the cool nights to have to use the AC..
I own a 2014 Primetime Tracer... thank you...